A Close Up Look at an Elusive and Endangered Species: The Least Bittern (lxobrychus exilis)

by: Donna Martin, Caretaker at the North, West and East Shoal Lakes IBA

Least Bittern – copyright Donna Martin

I am the volunteer caretaker of North, West and East Shoal Lakes Important Bird Area, which is located within the southwestern part of Manitoba’s Interlake Region. Identified as MB038, this IBA is approximately 15 km east of Lake Manitoba, in Manitoba, Canada.

The North, West and East Shoal Lake IBA is a landlocked drainage basin consisting of three large bodies of water. Land use surrounding this IBA is mainly grazing, with a small percentage used for forage crops. Open deciduous forests are found scattered around all three areas, mostly in early successional stages. In recent years, water levels have risen to an all-time high, which has affected land use surrounding all three lakes and has impacted the avian species that use this area for breeding and staging. The marshes associated with these lakes are mostly cattail marshes, which is prime habitat for least bitterns and other waders, waterfowl and marsh birds.

North, West and East Shoal Lakes IBA

Between 1985 and 1996, 46 pairs of Piping Plovers (1.5% of the Great Plains population) were found nesting here (IBA Canada, http://bit.ly/1ugivvD). However, they have not been recorded here since the early 1990’s (IBA Canada, http://bit.ly/1ugivvD). Historic records also identified large numbers of breeding American White Pelican, four species of grebe, Black-crowned Night Heron, and to a lesser extent, Common Tern, Double-crested Cormorant, Herring Gull and Ring-billed Gull (IBA Canada, http://bit.ly/1ugivvD). At one point, fall staging records documented over 100,000 Canada Geese and approximately 200,000 snow geese using this area, along with large numbers of waterfowl species (IBA Canada, http://bit.ly/1ugivvD). Also recorded were various species of shorebirds, using the area for staging during both the spring and fall (IBA Canada, http://bit.ly/1ugivvD).

A moderate shift in both the number and species using this area has been observed and hopefully with continued survey effort over the next few years, we will update and document the breeding bird data and staging usage for this IBA.

One of five juvenile Least Bitterns found in the North Shoal Lake area on Sept 15, 2014 – copyright Donna Martin

This year, we were excited to document two adult male Least Bitterns early in the breeding season. Observed by quite a few people, these two birds were identified in two different areas of the IBA. The first bird was found in the North Shoal Lake area and the second bird was spotted in the East Shoal Lake area.

Both adult birds were very skittish and although I saw both on most days I was out there, they would fly into the dense cattail reeds at the first sign of approach.

Adult male Least Bittern – copyright Christian Artuso

The Least Bittern is classified as a small heron of about 30 cm, just bigger than a robin. It breeds in marshes associated with emergent vegetation and needs some open, clean and clear water, as it hunts the marsh edges by sight. This bird is seldom seen but most often detected by call.

Listed by Manitoba’s Endangered Species and Ecosystem Act (ESEA) as an endangered species and considered nationally threatened by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC), it was a great bird to find associated with this IBA.

One of the five juvenile Least Bitterns found in the North Shoal Lake area – copyright Donna Martin

It was great to document the two adult Least Bitterns early in the season, but it was even more exciting to find 5 hatch year birds in early September.

Trips to the IBA revealed one Juvenile Least Bittern on September 6, 2014. Two juveniles were seen on September 10, 2014 and September 14 revealed three birds, all believed to be hatch year birds. On September 15, five juveniles were seen in the same area in North Shoal Lake. The juveniles found this year appeared more tolerant than the adults found earlier in the season, which allowed for some great photographic opportunities and documentation.

This was the first juvenile Least Bittern found on September 6, 2014 – copyright Donna Martin

The Least Bittern is protected under the Federal Species at Risk Act (SARA), Migratory Birds Convention Act, and the Manitoba Endangered Species Act.

The main threats to this species are mostly anthropogenic, with loss from destruction of habitat, shoreline development, wetland drainage and invasive species. It has a low threshold and does not tolerate human disturbances well and will leave suitable habitat if human activities become too great. Climate change could also be a threat, as it can alter water levels, which can alter habitat.

Close up view of a Least Bittern seen at North Shoal Lake, September 15, 2014 – copyright Donna Martin

The Least Bittern was an exciting species to find this summer. Efforts next year will include trying to document breeding evidence, behavior, density and numbers of young birds of this species.